Nagamasa Azai

Nagamasa Azai (1545-28 August 1573) was the daimyo of the Azai clan of Omi Province during the Sengoku period. He was the brother-in-law of Nobunaga Oda after marrying his sister Oichi in 1564, but he became enemies with him after Nobunaga attacked Nagamasa's ally, Yoshikage Asakura. Nagamasa was defeated at the Battle of Anegawa in 1570, and he was slain at the Siege of Odani Castle in 1573.

Biography
Nagamasa Azai was the son of Hisamasa Azai, the daimyo of the Azai clan of Omi Province. In 1560, his father was pressured by his retainers to abdicate in favor of his son, and Nagamasa battled rivals Yoshikata Rokkaku and Tatsuoki Saito. In 1560, he assisted Nobunaga Oda (a fellow enemy of the Saito clan) at the Battle of Okehazama, and, seeing Nagamasa's potential, Nobunaga had his sister Oichi marry him. In 1570, when Nobunaga declared war on the Asakura clan of Echizen Province, Nagamasa discerned that his clan's traditional allies under Yoshikage Asakura needed his help more than Nobunaga did, and he sided with the Asakura against the Oda. In 1570, the Azai-Asakura army was defeated by the Oda-Tokugawa army at the Battle of Anegawa, and Nagamasa took part in coalitions against Nobunaga for the next three years. In 1573, Nobunaga besieged Nagamasa at Odani Castle, and Nagamasa chose to commit seppuku alongside his father due to the impossibility of victory.